Ion implantation systems are used to dope semiconductors with impurities in integrated circuit manufacturing. In such systems, an ion source ionizes a desired dopant element, which is extracted from the source in the form of an ion beam of desired energy. The ion beam is then directed at the surface of a workpiece in order to implant the workpiece with the dopant element. The ions of the ion beam penetrate the surface of the workpiece to form a region of desired conductivity, such as desired in the fabrication of transistor devices in a semiconductor wafer. A typical ion implanter includes an ion source for generating the ion beam, a beamline assembly including a mass analysis apparatus for mass resolving the ion beam using magnetic fields, and a target chamber containing the workpiece to be implanted by the ion beam.
In ion implantation processes, the angle at which the ion beam approaches the workpiece (also called an implant angle) is fixed at a particular angle during the ion implantation. It is becoming common, however, for devices being formed on a workpiece 10, such as illustrated in FIG. 1, to have three-dimensional (3-D) structures 12, wherein uniform ion implantation across all dimensional surfaces of the 3-D structure is desired. For example, in a FinFET device 14, variations of the incident angle of an ion beam 16 to the workpiece 10 is desirable in order to implant both trenches 18 and sidewalls 20 of structures 22 of the FinFET device.
Conventionally, in order to implant ions into the workpiece 10 at different incident angles, the ion implantation is temporarily halted or idled (with the ion beam 16 not being directed toward the workpiece), and the workpiece is mechanically tilted (e.g., illustrated by arrow 24) relative to the ion beam 16, thus varying or modifying the angle of incidence of the ion beam to the workpiece. The ion beam 16 is then again directed toward the workpiece 10 and the workpiece is implanted at the modified angle of incidence. In FinFET devices, where complex 3-D structures can be present, this may require two or more different incident angle variations in order to adequately implant the trenches 18 and/or sidewalls 20 of the structures 22. Heretofore, systems and methods for achieving angle variation have been to pivot the workpiece 10 around an axis such that the ion beam 16 strikes the workpiece at a different angle.
As such, since the angle of incidence is mechanically varied at the workpiece 10, throughput associated with the operation of the ion implantation system can be adversely affected, as substantial time can be spent with the ion beam not impacting the workpiece while the angle of incidence is mechanically varied.